1. Field of the Invention
The present invention relates to a retainer, and more particularly to a roller retainer, which can prevent the rollers from contacting each other, and keep the non-loading surfaces of the rollers from colliding with and rubbing against the track while the loading surfaces of the rollers can still contact the track, consequently reducing the noise and assuring the moving direction.
2. Description of the Prior Art
Linear guideway and roller screw are used more and more widely in modern industries. In addition to its high precision transmission performance, the linear guideway and roller screw also have many other advantages, such as low friction loss, high ratio of energy conversion, low noise, high rigidity and wear-resistance. Therefore, it is self-evident that the linear guideway or the roller screw is very important to various industrial mechanisms.
Normally, rollers are one of the frequently used rolling elements of the linear guideway and the roller screw, in order to enable the rollers between the subassemblies to circulate endlessly, roller retainers are disposed on the rollers. Accordingly, the present industry emphasis is focused on how to research and develop the more competitive roller retainers.
FIGS. 1-3 show two frequently used conventional roller retainers; please refer to the following descriptions:
FIG. 1 shows a conventional roller retainer disclosed by JP Pat. No. 2002-48143, wherein an annular groove 11 is formed in the middle portion of each roller 10 of a roller screw, and every other roller 10 is disposed with a space ring 12. Since the annular groove 11 formed in the middle portion of the roller 10 is provided for receiving the protrusions of the space ring 12, the space ring 12 disposed on every other roller 10 can separate the rollers from each other, and prevent the rollers from colliding each other. The aforementioned roller retainers still have the following shortcomings:
First, since the rollers 10 are positioned on the tooth-shaped track 13 between the roller screw and the nut, the screw and the nut will not only contact the loading surfaces of the roller 10, but also contact the non-loading surfaces of the rollers, thus causing the collision and the friction therein, and influencing the moving direction of the rollers 10, as a result, it cause attrition and stress loss.
Second, in order that the space rings 12 disposed on the rollers 10 can run smoothly along the tack 13 between the roller screw and the nut, the track 13 should be additionally formed with a groove 14. Since the groove 14 is formed in the loading surface of the rollers 10, the contacting length of the rollers 10 is reduced and the load capability of the product is consequently decreased.
To solve the aforementioned problems, another internal circulation roller screw was developed. Please refer to FIGS. 2-3, which show a conventional roller retainer disclosed by U.S. Pat. No. 6,575,632, wherein a stopping annular retainer 16 is diagonally mounted on the roller 15 and is disposed in the V-shaped track formed between the roller screw (not shown) and the nut 17. The stopping annular retainer 16 is used to prevent the collision between the rollers or the energy loss caused by attrition, and a groove can be formed to avoid the loading surfaces of the roller 15 contacting the roller screw and the nut 17. This improved technology appears to have solved the forepassed problems, but it still has the following problems:
First, since the stopping annular retainer 16 is only mounted along a single diagonal of the roller 15, it must enable the non-loading surfaces on both side surfaces of the roller 15 to keep a distance from the roller screw or the nut 17. But the roller will apply a torque to the stopping annular retainer 16 while rotating, consequently, the roller 15 will incline to the non-loading surfaces thereof, thus the stopping annular retainer 16 is difficult to position, and likely to fall off, this technology is quite easy to cause the stopping annular retainer to fall off and the rollers to be jammed.
Second, since the stopping annular retainer 16 is only disposed along a single diagonal of the roller 15, a certain thickness and a material stress are required for the stopping retainer 16 to hold the roller 15 stably, otherwise the disengagement of the roller is unavoidable. But if the thickness of the stopping retainer 16 is excessively thick, the space between each roller 15 will be increased, and consequently the number of rollers 15 and the load capability will also be reduced.
Third, rollers disposed in the liner mechanisms (such as roller screws or liner guideways) must perform re-circulation motion, but each of this conventional rollers 15 is only diagonally disposed with a single stopping annual retainer 16, since the roller 15 must overturn during the circulation, the stopping annual retainer 16 disposed on the single diagonal of the rollers will lose the effect of abutting against and separating the rollers 15, and cause the non-loading surfaces of the roller 15 to contact other components. Consequently, the collision and the attrition will still occur during the overturn of the rollers 15.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.